The present invention relates generally to bicycles and, more particularly, to shock assemblies that are constructed to facilitate controlled movement between movable members of a bicycle, such as a frame and a wheel assembly.
The primary structural component of a conventional two-wheel bicycle is the frame. On a conventional road bicycle, the frame is typically constructed from a set of tubular members assembled together to form the frame. For many bicycles, the frame is constructed from members commonly referred to as the top tube, down tube, seat tube, seat stays and chain stays, and those members are joined together at intersections commonly referred to as the head tube, seat post, bottom bracket and rear dropout. The top tube usually extends from the head tube rearward to the seat tube. The head tube, sometimes referred to as the neck, is a short tubular structural member at the upper forward portion of the bicycle which supports the handlebar and front steering fork, which has the front wheel on it. The down tube usually extends downwardly and rearward from the head tube to the bottom bracket, the bottom bracket usually comprising a cylindrical member for supporting the pedals and chain drive mechanism which powers the bicycle. The seat tube usually extends from the bottom bracket upwardly to where it is joined to the rear end of the top tube. The seat tube also usually functions to telescopically receive a seat post for supporting a seat or saddle for the bicycle rider to sit on.
The chain stays normally extend rearward from the bottom bracket. The seat stays normally extend downwardly and rearward from the top of the seat tube. The chain stays and seat stays are normally joined together with a rear dropout for supporting the rear axle of the rear wheel. The front wheel assembly is commonly mounted between a pair of forks that are pivotably connected to the frame proximate the head tube. The foregoing description represents the construction of a conventional bicycle frame which of course does not possess a suspension having any shock absorbing characteristics.
The increased popularity in recent years of off-road cycling, particularly on unpaved terrain or cross-country, as well as an interest in reducing discomfort associated with rougher road riding, has made shock absorbing systems a desirable attribute in biking system. A bicycle with a properly designed suspension system is capable of traveling over extremely bumpy, uneven terrain and up or down very steep inclines. Suspension bicycles are less punishing, reduce fatigue, reduce the likelihood of rider injury, and are much more comfortable to ride. For off-road cycling in particular, a suspension system greatly increases the rider's ability to control the bicycle because the wheels remain in contact with the ground as they ride over rocks and bumps in the terrain instead of being bounced into the air as occurs on conventional non-suspension bicycles.
Over the last several years the number of bicycles now equipped with suspension systems has dramatically increased. In fact, many bicycles are now fully suspended, meaning that the bicycle has both a front and rear wheel suspension systems. Front suspensions were the first to become popular. Designed to remove the pounding to the bicycle front end, the front suspension is simpler to implement than a rear suspension. A front suspension fork is easy to retrofit onto an older model bicycle. On the other hand, a rear suspension will increase traction and assist in cornering and balance the ride.
During cycling, as the bicycle moves along a desired path, discontinuities of the terrain are communicated to the assembly of the bicycle and ultimately to the rider. Although such discontinuities are generally negligible for cyclists operating on paved surfaces, riders venturing from the beaten path frequently encounter such terrain. With the proliferation of mountain biking, many riders seek the more treacherous trail. Technology has developed to assist such adventurous riders in conquering the road less traveled. Wheel suspension systems are one such feature.
Even though suspension features have proliferated in bicycle constructions, the performance of the suspension as well as the structure of the bicycle are often limited to or must be tailored to cooperate with the structure and operation of the shock. Commonly, as the bicycle traverses uneven terrain or during aggressive riding, the overall length of the shock shortens and thereby compresses a volume of air or gas enclosed by the shock. As the shock continues to shorten, a piston supported by a compression rod continues to compress the fluid as the size of the chamber continues to get smaller. As compression of the gas continues, the shock becomes progressively more resistive to allowing continued shortening of the shock. That is, the compressibility of the gas contained in the shock results in the shock feeling progressively stiffer as the overall shock length continues to shorten. Such operation detracts from the range of movement of the shock wherein a desired shock performance can be attained and/or requires greater shock lengths to accommodate a desired range of motion dampening operation.
Therefore, there is a need for a shock system that is more responsive to loading across a wider range of the overall compressibility of the shock. There is a further need for a shock system that can provide a variety of shock performances without otherwise interfering with the mounting of the shock to the bicycle.